It is well-known that it is possible to impart energy to a multiphase fluid or to a mixture of gas and liquid by means of various machine types.
Whatever the design of the rotodynamic pumps used, and more particularly single-phase type pumps, good results are obtained when the value of the gas-liquid volume ratio under real given pressure and temperature conditions (GLR in abbreviated form) of the fluid is low.
Pumping of a liquid-gas mixture by means of radial impellers is thus generally limited to gas proportions below 20%. This limit can be brought to about 30% in the case of radio-axial impellers and to about 40% with axial impellers.
The prior art also describes pumping devices having characteristics suited to pumping of a multiphase fluid. For example, the applicant's patent FR-2,665,224 describes a geometry of the cross-section of flow for a multiphase fluid that is delimited by two successive blades, suited to impart energy to a multiphase fluid in order to compress fluids whose GLR value ranges for example between 0 and 20.
However, the pumping or compression efficiency for such a fluid varies considerably according to the conditions in which the fluid notably is. This efficiency tends to decrease when the two-phase fraction increases and when the ratio of the density of the gas to the density of the liquid decreases. Besides, the single-phase performances of these impellers that serve as a reference for determination of the two-phase performances are substantially lower than those of radial impellers, in particular the efficiency and the manometric head delivered per stage.
Furthermore, it is often necessary to use several machines positioned in series in order to obtain the desired compression ratio.
Using several single-phase machines (pump and compressor) or several multiphase type machines leads to bulky and expensive compression installations.